Depositional scenarios Bay mud
decomposed diatoms 1 component of bay mud
bay muds originate 2 generalized sources. first alluvial deposits of clays, silts , sand occur streams tributary given bay. extent of these unconsolidated interglacial deposits typically ranges throughout given bay extent of historical perimeter marshlands. second, in periods of high glaciation, deposits of silts, sands , organic plus inorganic detritus (e.g. decomposition of estuarine diatoms) may form separate distinct layer. bay muds important time records of glacial activity , streamflow throughout quaternary period.
some depositional formation quite recent, such in case of florida bay, of bay mud has accumulated since 2000 bc, , consists of decayed organic material. in case of florida bay these bay muds can accrete as 0.5 2.0 centimeters per annum, although dynamic equilibrium of erosion, wave action redistribution , deposition complicate net rate of layer growth. in case of bristol channel in united kingdom bay, mud formation has been occurring @ least since eemian stage (known sangamonian stage in north america), or 130,000 years ago. in other cases such san francisco bay, deposition has been interrupted sea-level changes, , strata of vastly different vintages found. in san francisco bay area, these called young bay mud , older bay mud geologists. human activities can affect deposition; close half of young bay mud in san francisco bay placed in period 1855–1865, result of placer mining in sierra nevada foothills.
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